Balancing system for aircraft



J. P. TARBOX BALANCING SYSTEM FOR A IRCRAPT Aug. 14, 1923.

Original Filed June 20', 1918 2 Sheets-Sheet l I awvewt o'c J. P. TARBOXBALANCING SYSTEM FOR AIRCRAFT Aug. 14, 1923.

Original Filed June 20, 1918 2 Sheets-Sheet 2 I LOWER LIMIT RESULTANTFORCE CENTER OF PRESSURE 5 10 15 '20" 25' so ANGLE 0F lNClDENCE.

% INVENTOR Patented Aug. 14, 1923.

UNITEDTSTATES PATENT. OFFICE.

JOHN P. TARBOX, OF GARDEN CITY, NEW YGRK, ASSIGNOB. TO TARBOX SAFETYAIRCRAFT COMPANY, A CORPORATION OF DELAWARE.

BALANCING SYSTEM FOR AIRCRAFT.

To all who-m it may concern:

Be it known that I, Jon's P. Tanuox, a citizen of the United States,residing at warden City, in the county of Nassau and State of New York,have invented certain new and useful Improvements in Balancing Systemsfor Aircraft of which the "following is a specification.

My invention relates to balance systems for aircraft and particularly tolateral balance systems of the type disclosed in my issued Patent No.l.2; l9,636 in which the dif ferentiation or" the pressures of air rushon opposite sides of the craft combined with the force otgravity isutilized to effect control of the lateral. balance; l/Vhile having thisspecial relation however it will be immediately obvious to those skilledin the art and having an understanding of the present invention that itis not only applicable to the particular systems with which it has beenassociated, but also may very readily be utilized connection with othersystems of longitudinal and lateral control.

In my application aforesaid, there were disclosed a pairof vertical axisailerons connected together as by a cable to partake of difl'erentialmovements in response to (lif Hy present invention is an improvementdirected particularly to a system embodym ailerons oi. the transverseaxis type.

The improvement, however. is also appli-' cable to systems embodied byailerons of other types. including the vertical axis type. hen aileronsot the transverse axis type are connected together for differentialaction as above set forth. I have toun d that they have when set atextremely low angles of incidence a tendency to permit the inducement ofoscillatory orpnmpinsz action. Careful adjustment. or the provision ofauxiliary damping surfaces or vanes as provided for in m earliersystems. will each prevent this. but I have found that the necessity ofclose adjustment. and the careful proportioning of Application filedJune 20, 1918, Serial No. 24:0,982. Renewed January 12, 1923.

maximum etiiciency which, if the aileron is,

of a section the same as or similar to the section of the mainsupporting surfaces. is usually a very small angle. According to myinvention 1 make this angle different preferably considerably greaterand find that the beneficial effects are realized in the greater degreeas the angle of setting approaches the critical angle. I also make theaerofoil section different. The aerodynamic reason fo this phenomena isfound to be twofold. First in balancing: systems of the type set forth.there are equated moments of resistance. \textremely low angles theresistance increases on both sides of said minimum angle. Obviously thisbrings about moments noncontormable and incommensurate to theunbalancinn forces. Secondly at a low angle in the vicinity oi the angleof minimum re sistance. there is a substantial, sudden and extensivetravel of the center of pressure. Suclrtravel changes immensely thelever arm of the moments of both resistance and lift (andcorrespondingly of the resulting total torcelfi These irregularitiesinduce oscillations. Now by giving the balancing surfaces comparativelylarge positive angles in their normal range, of movement they do notreach at their upper extreme or at their minimum angle. the angles ofminimum re s stance or angles of substantial and sud- Referring to-thedrawing. Fig. 1. is a per no spective diagrammatic showing of one em outthe normal range ofmovemenhthere fore,

supporting" surface and given a nornmil angle o line hodiment of myinvention, Fig. '2 a similar viewo'f another, l igqil a diagramillustrat ing the relation of the ailerons to the supporting surfaces;Fig. 4t-

set of characteristic Curves oivthe modern aeroloil.

Referringfirst to Fin 1, h) is the main it and the rightaiml left handailerons or lqmlanoing sin-laces illustratedthey are the transverse axistype the axis being, deshmated hv the dash and (lot lines passing in trthe lead;- ing edges. This axis may he constituted. by any Form of shaftor an form of hearin in theproper transi 'erse relatimi to the aileronsll and L and havi suitable snpport from the main support a surface J)01' from any i uetore associated th'm'eavith and constitutino arelatively fixed body as respects surfaces R and L. P reason of locationnear the leadin; edqe o'f'lthc: sur-" *faoe; the axes are in zulva. reof the pointof extreme 'lorivare movement o? the renter of pressure innormal trm'el. it rahle ll interconnects the surfaces at the rear o 5the axe-s heing gnided over suit ole A second cahl, 13, in i shown indotted lines 'f in the ailerons in normal posf ion against the action.of gravity r-hile the aeroplane is standing. 7 with cahle ll, by

Connected sector 1-1, in this on a srhstantiall; ver tic-ally disposeda. is are 2' ma s 16 arrd a: damping vane 17 adinstahl y nmnnted on armslSand 19 respectively carried h) axis 15. The i to from any lixed mrt oithe machine or *t'rom" any part fixed. relative to snri'aces and L orthe interconncctiinr cable ll. (or cahle 13) with which parts lei, 1:6,l'Tinay he coin li-ined 'f'he' ailerons ll a'mllj are as shown in lZence in eitcess of the normal angle incid nce o: main supporting-1'surface 10. indi in Fig. 3 the principal 'snppoi is set at 3 but theFiala and L are set normallv v :foi-l section of the-sari in a 'en instnct) the r princi' jal 'sn iportin z sin illustrated them asof (ll mosteflirientlv from, all and? ticularlv that o? :zdninmm-head stanre) atthe larger angles 0? which the)" are sol. Thus ave: will insume that thearr-lion 0. surface shown in Fig. operates at if) at considerahlvgreater efliciene iar would a similarli'" dhosed section oi the mainsurface 10. Surface will operates most efliciently at neigldyorhood of3.

This normal setting cable 1.1 (or ll and L l. vanel? is parallel to theline 0 upon the opposite sioes 0' the machine act also upon thebalancing; sartaws h. and L and. they in turn partake of tlitl'erentialmovement by reason oi interconl'iectirig czhle 11, the mass 16 and thevane l7 moving inunison (or in synchronism) therewith. The sector l lisof courseappropriatelv curved and the sections oil cahle ll so connectedtherewith that the leverage allordecl. hy the sector is maintained thesame. In action as thus organized l find the system to he completelypositive and dead-heat; and. yet, there is no change so small or sosubtle that it escapes prompt detection and correction. In other wordsthe notion is at once sensitive, positive and stea d vf Referring noW tothe diagrams oi Fit. 4, the relation of the differential sell actingsnrita :es R and L to the line oi :"liggfhtjand the relation oi. thenormal raiwe of operative nu ement to the angles of n'nnininn'iresistance and substantial cl'lan re of the center vol. pressureLlearlj; appears. The normal range is indicated by dotted lines. It willl 2 seen that the upper or small ang e limit this range lies on tl atside of the angles 0'? minimum resistance and snhstantinl chan ire incenter of pressure tovvard the 'sril'ical'angle. The lower range mag lieon either side of the critical. anghg although it should preferably notvery greatly exceed it. I ha e found the position ol the lower limil 'tohe relatifi'ely innnaterial 'within reasonahle 'ran e oi the criticalangle. In actual tests made, snitahle stops were provided to regulatethe range ort'rmmeinent hetween de sirthle limits. I

The dimensions, contours sections and in terconnections of the parts maybe varied to suit the particular machine upon which the systeminstalled; Adjustments to secure any degree of sensitivity,]'iositiveness and steadiness may likewise be made. The action of theadjustable mass 16 and vane 17 is-identical with that disclosed in myissued Patent No. 1.239133? The fact that these elements are located atan intermediate pointinstead of at the extremities of the n'la'chine(lo-0S not change the fundamental flunetioning.

The form of Fig. 2 differs from the form of Fig: 1 in that surfaces R"(and L not shown) are made very small. in size and constituted merepilot surfaces. As inclicatecl. they are mounted upon. small still) shr.ts 2O iournaled onthe ends of ma n sop portlng surface 10 andinteroonnectedhf cables 21 for differential movement similar to thesurfaces it and L The relative normal setting as respects the mainsupporting surface 10 is the same, that is, their normal angle ofincidence is greater. CablesQl. are connected to elements 1d, 15, 16,17similar to those of Fig. l. in addition, however, cables 21 areconnected by lever 22 with the stem of the control valve (or equivalentcontrolling element) of a fluid operated (or other) servo motor 25. Themotor illustrated is of the fixed piston type as indicated by the fixedpiston rod 26, the body 25 moving on the rod 26. This type is well knownto the art and its remaining details need not be shown. The movable body25 is connected by the usual operating cables 27 to the usual balancingailerons A at the trailing edge of the main supporting surface 10.

The operation is essentially similar to the operation of the systemdisclosed in Fig. 1. Instead however of exercising controlling forces ofsuch size as to themselves effect balance of the machine, these pilotsurfaces (R and L) act upon the control member 24: of the servo motor 25to effect balance ofthe machine through the movements of the ordinaryaileron A in such direction and to such extent as necessary forcorrection of balance. I

There are yet other embodiments of which my invention is capable, manyothers. All such embodiments should fall within the scope of theappended claims.

1. In an aircraft, a lateral balancing system, comprising differentialself act ing laterally disposed supplemental surfaces having each apositive normal range of angular movement so fixed in position andextent with respect to the line of flight that both upper and lowerextremes of normal movement lie on that side of its angle of center ofpressure reversal toward its own critical angle.

2. In an aircraft having a principal supporting surface having adeterminate normal angle of incidence with respect to the line offlight, together with differential self acting relatively movablelateral balance control surfaces, having normally each an angle ofincidence with respect to its own regional air rush numerically greaterthan the angle of incidence of said principal sup porting surfaceaforesaid, together with air rush actuated damping means affccting thedifferential movement of said surfaces.

3. An aircraft comprising a main supporting member which constitutes thelift-v ing body of the craft, and an automatic balancing system thereforcomprising balancdevices upon each side of said main supporting memberand presentmg co-operating transversely extended surfaces ar ranged tobeaeted upon normally during flight by'air pressure to producetorques inopposite directions about the longitudinal axis of the craft, saidbalancing devices being connected toeach other and each re sponsive totemporarily preponderating pressure thereon to increase the torque of'theother, and having associated therewith a mass acted upon by gravitywhen the craft is unbalanced to alter the normal torque relations aslong as the craft remains unbalanced, said main supporting member havinga determinate normal angle of incidence with respect to the line offlight while said balancing devices have normally angles of incidenceeach with respect to its own regional air rush numerically greater thanthe angle of incidence of said supporting member aforesaid and dampingmeans affecting the movements of said balance devices.

hln an aircraft having a principal sup porting surface having adeterminate normal angle of incidence, together with differential selfacting relatively movable lateral balance control surfaces, having apositive normal setting of the angle of incidence materially greaterthan the normal angle of said supporting surfaces, said lateral balancecontrol surfaces having a longitudinal aerofoil section whose lift overdrift ratio at the greater normal. angle of incidence of said controlsurfaces is greater than the lift over drift ratio which can be derivedfrom the adjacent section of the principal supporting surface at thesame greater angle of incidence.

5. In an aircraft having a principal supporting surface having adeterminate normal angle of incidence with respect to the line offlight, together with differential self acting relatively movablelateral balance control surfaces having normal angular range of movementof such extent and so fixed with respect to the line of flight that atits upper extreme the surface is at a positive angle adjacent to buttoward the critical angle from the angle of marked chan e in position ofthe center of pressure.

- 6. in an aircraft having a principal. supporting surface having adeterminate normal angle of incidence, differential self act- .ingrelatively movable lateral balance con-' trol surfaces having arelatively large-normal range of change of the angle of incidence intheir normal balancing function, which range is of such extent and sofixed with respect to the line of flight that its upper extremity givesto the surface an angle lying on that side of theangle marking minimumresistance which is towards the critical angle.

7. In an aircraft having a principal sup porting surface having adeterminate normal angle of incidence with respect to the line offlight. a self acting balancing system therefor comprisingdifferentially connected relatively movable lateral balance control ofthe center of pressure, but at an angle on surfaces relatively movableabout transthat side of said angle of substantial travel 10 verse axes,Which difierentially connected of the center of pressure lying towardthe surfaces have a normal range of movement critical angle.

so fixed in position and extent with respect Intestimony whereof Ihereunto all ix my to the line of flight that at the uppermostsignature.

limit of normal movement neither balance" surface is at the angle ofsubstantial. travel JOHN P. TARBOX.

